These studies will investigate the role of angiotensin II on central nervous system (CNS) receptors which regulate blood pressure and the possible role played by angiotensin in sustained hypertension of CNS origin. All experiments will be conducted in conscious sheep which are in normal correspondence with their environment and have not undergone recent surgical intervention. Angiotensin II, at physiologically feasible levels, will be administered via the cerebral blood supply and also into the CSF to determine if qualitative differences exist in the development of hypertension secondary to these different routes of administration. The temporal relationship between changes in blood pressure and changes in salt and water intake will be determined to elucidate possible contributing factors to any blood pressure changes. Peripheral cardiovascular variables including cardiac output, total peripheral resistance, renal blood flow and renal resistance will be determined to understand whether renal, cardiac or peripheral resistance factors are important in this type of hypertension. The relationship between chronic, low-level angiotensin II administration and vasopressin and aldosterone secretion and possible contributors to the blood pressure changes observed will be studied in the same animals. Localization of angiotensin sensitive areas within the cerebral ventricular system will be studied by use of multiple ventricular cannulae and lesioning studies. Possible involvement of adrenal catecholamines and mineralocorticoid secretion will be investigated by adrenalectomy, adrenal denervation and use of competitive antagonists of aldosterone.